| The fates of metals (e.g. Fe, Cu, and Zn) have been studied in soils at a former tannery site. Soil at the site varied in degree of water saturation, oxidation-reduction state, organic matter content, and metals concentrations. These conditions afforded the opportunity to study how biogeochemical soil conditions affect the formation, alteration, and sequestering ability of environmentally reactive metal binding phases. Sequential chemical extractions (SCEs) and porewater chemistry were used to determine metal partitioning within soil, and between solid and fluid phases, respectively. Information gained from SCEs, developed for oxic systems, was evaluated for anoxic systems.;In oxic soils, the easily reducible (ER - reactive Fe oxides), moderately reducible (MR - Fe oxides), and basic oxidizable (OX1 - organic matter) were the most important sequestering phases of metals. In anoxic soils these three phases were also important, but the mineralogical substrates comprising the ER and MR phases were unclear. Detailed analyses of meta-stable, water saturated, anoxic soils including: porewater redox potential determination; geochemical modeling; SCEs; acid volatile sulfide extractions; magnetic mineral fractionation; and x-ray diffraction, were preformed to determine mineralogical substrates comprising the ER and MR phases. SCEs performed on pure minerals, identified in anoxic soils, demonstrated that the SCE method used could not selectively distinguish between substrates that were found to comprise the ER and MR phases. |
